The present invention is directed to novel emulsifiers for use in the production of stable, water-continuous (oil-in-water) emulsions from crudes, tars and bitumens. Of particular emphasis is the formation of emulsions that have long-term stability and more particularly emulsions based on the use of certain novel surfactants to emulsify bitumens obtained from tar sands such as Syncrude bitumen obtained from Athabasca tar sands.
Crudes produced in the field may vary widely in respect to water content which depends in part on the water used to produce a hydrocarbon crude. Where the crude is formed in fields with a strong water drive, the water cut or amount of water associated with the crude produced can be as high as 95% of the total produced stream.
The water present in a produced stream can be classified into two categories: bound water and free water. Bound water is that water which is locked up in the crude as a water-in-oil emulsion. Separating this water from the stream typically requires appropriate heating, mixing and chemical demulsifiers. Free water is that water which is relatively loosely held by the crude and can be removed simply by heating the stream to a suitable temperature.
Certain bitumens or tar sands, by contrast, and are essentially water-free. They disadvantageously have high viscosities; e.g., 20,000 cp at 100.degree. F. and 300 cp at 200.degree. F. This makes their transport at conventional pipelines at ambient temperatures impossible.
The use of a solvent diluent (e.g., 30-50% by volume) is unsuitable due to cost and long-term unavailability of a low-viscosity fluid and the cost of separation and recycle to origin. A need exists to transfer bitumens and other hydrocarbons over long distances by conventional pipeline technology to existing facilities at costs consonant with oil production.
Water-in-oil emulsions have too high a viscosity and normally higher than the dry oil itself. By contrast, oil-in-water emulsions afford viscosities at levels where pipeline transmission is economical. In cold environments, a problem would still exist, however, in phase destabilization, freezing or an increase in viscosity to a level too high for pipeline transmission. The present invention is directed to the solution of this problem.